(a) Technical Field
The present invention relates to an interface circuit for detecting a fault in a resolver and a method of detecting the fault in the resolver using the same.
(b) Background Art
A hybrid electric vehicle or electric vehicle typically employ a driving motor, such as a permanent-magnet synchronous motor (PMSM), in order to obtain driving force to propel the vehicle in a forward or reverse direction. These motors typically include a one or more permanent magnets that apply a magnetic and reluctance torque to a shaft connected to the driving motor.
In order to achieve high-performance control while applying magnetic torque and reluctance torque to a rotor of the driving motor consistently, information regarding the speed of the driving motor and a position of the rotor is required. Conventionally, an environment-friendly vehicle uses a resolver with excellent environment-resistance and a wide range of usable temperatures in order to detect the position of the driving motor.
FIG. 3 is a schematic view showing a configuration of a conventional resolver. The resolver 13 includes a stator 13 wound with a coil inside a housing 11, a rotor made of permanent magnet and installed inside the stator 13, input terminals R1 and R2 to which AC voltage is supplied, first output terminals L1 and L2 that output a sine wave signal therethrough according to a position of the permanent magnet rotor 13 having north pole to (N-pole) and south pole (S-pole) and a second output terminals L3 and L4 for outputting a cosine wave signal therethrough.
When the rotor 15 is rotated upon supplying an AC voltage to the stator 13 wound with the coil through the input terminals R1 and R2, a magnetic coupling coefficient between the stator 13 and the rotor 15 is varied, so that an amplitude-modulated carrier frequency having a sine wave form is output through the first output terminals L1 and L2 as the sine wave signal and an amplitude-modulated carrier frequency having a sine wave form is output through the second output terminals L3 and L4 as the cosine wave signal.
Thus, a rotation angle θ of the resolver may be determined by using the phase variations of the sine and cosine wave signals output through the first and second output terminals L1, L2, L3 and L4. In addition, an excitation signal is applied to the input terminals R1 and R2 of the resolver 10 through a lead wire, and the first and second output terminals L1, L2, L3 and L4 are connected to an RDC (Resolver to Digital Converter) through the lead wire.
FIG. 4 is a circuit diagram showing an inverter system of a hybrid or electric vehicle to which the resolver is applied. The inverter system used in the hybrid or electric vehicle in particular includes a power module (IGBT (Insulated Gate Bipolar Mode Transistor)) 1, a DC-link capacitor 2, a DC-link voltage sensor 3, a DC-link voltage sensing circuit 4, a to current sensor 5, a current sensing circuit 6m a computing processing unit (CPU) 7 and a control/gate board 8.
The power module 1 transfers electrical current between a battery and the PMSM and the DC-link capacitor 2 absorbs a ripple effect generated by the DC voltage from the inverter operation so that the ripple effect is prevented from being transferred to the battery. The DC-link voltage sensing circuit 4 processes the output from the DC voltage sensor 3 in order to adjust the output into a range in which the output may be input to an analog/digital converter, and prevents a voltage measurement error from occurring.
Additionally, the current sensor 5 measures an AC current of the invertor which can be used for inverter control. The current sensing circuit 6 processes the output from the current sensor 5 in order to adjust the output into a range in which the output may be input to the analog/digital converter, and prevents a current measurement error from occurring. The CPU 7, in which inverter control software is installed, controls the overall operation of the inverter by using the measured physical quantity. The control/gate board 8 provides spaces in which components used for the inverter-control of the CPU 7 and any other circuits are mounted thereon.
In the inverter system described above, the resolver provides information to the control system regarding the position of the motor rotator, so that the control system of the hybrid or electric vehicles is able to accurately control the motor. However, if the resolver itself fails due to a short circuit, it is impossible to detect the any issues in the motor and as a result the vehicle may be inoperable depending on the circumstances.